Got my truck back my mechanic put in fresh oil and added 3 bottles of the modifier:additive. I think he feels bad he hasn’t corrected the problem and didn’t charge me for this. I’m a long time customer and he’s a real stand up guy. We’ll see what happens. Thanks to everyone who gave advice, I appreciate it 😋

 

Well, with new fluid 3 friction modifiers may not be enough in there, just like before
If it is chattering you will need 4 or 5
You may have to suck some fluid out, in order to put some more modifier in it

 

Yes, we talked about that, and we'll add more if needed. Thanks for your advice!

 

You were right, it still chattered, my mechanic added 3 more friction modifiers, so we have 6 in there now, and he did have to suck some fluid out to add more modifier. He said try it for a week. Hope this does the trick.

 

The suspense is killing me, how was the ride home, any noise?
I usually do a few figure eights in a parking lot to get the modifier distributed in the oil and test it out

 

So far so good my mechanic did the figure 8 thing. No noise but never had any noise he said try it for a week to try it and stop back then we’ll square up

 

Well the vibration is still there, I will stop back, any idea's, more additive/modifier ? We have 6 in there now, thoughts ?

 

Friction modifier is for chatter (clutch pack chatter and related noise)
Vibration is not it
You will need to explain the exact where and when this vibration occurs
Rear axles themselves, do not vibrate, has been my experience
In Screwell, they used to have us check for ring gear and carrier runout (never seen it) Axle flange runout etc.
You are not going racing right? (putting 1000 HP to the ground) That will try to deflect the gearset, bend the axles and warp the carrier
You had better be checking the wheels for runout and the tires (the spec for radial runout of the tire and wheel is only .060)
The lateral runout is just as important (any tread deflection, from straight true is no good) Slipped belt on tire etc.

 

So this vibration occurs at a stop then making a left hand turn. No noise that I’ve ever heard just a subtle vibration like going over a washboard road only lasts into the turn then it fine it will sometimes happen turning right but not that often

 

You are describing clutch pack chatter, if on turns, going slow around a corner
Only lasts into the turn (need to see how bad this is for myself almost) Try putting some weight in the bed, check the tires for runout
So doing repeated figure eights at some speed causes no vibration
It is only from a stop then occurs just for a moment into the turn
That means to me, you may be tuned into this little vibration, and no cause or cure for it exists
Meaning once you get the vibration so many times it may never go away for you (it might be normal)
Need to examine the rear tires for runout and have another tech give a second opinion
I got a feeling the truck if fine, and you are tuned into this vibration bad enough that, there may be no remedy
Having it feel like you are going over washboards is not normal
Meaning the truck might not be fine
Get a second opinion and go on a road test with the tech
Do it at a Ford store where they might have a few master techs
Should be well worth the hundred bucks at this point
Better yet, pay nothing and tell dealer you are considering an upgrade and they will take and drive your truck to determine trade in value
While you are driving theirs, they will have someone looking at yours, usually
They might get back to you and say just numbers or they might shoot your truck down and tell you why

 

Interesting, tire runout, I had this rear end problem since I bought the truck, and have put on 40,000 miles, the truck has a new set of tires on it, This problem happened with both sets of tires. Like you said I may just live with it. I appreciate all you knowlege, and trying to help me.

 

Give it a 600 mile break in period
It may just go away completely

 

Good news that problem did go away. I only put about 80 miles a week on the truck so you said give it some time and you were right on. Thanks for all your advice. Scott

 

This rear end vibration is back, my mechanic thinks moisture is getting in somehow and causing this problem Anyone have thoughts on this ?

 

CHATTER going around a corner is Friction modifier related.... VIBRATION has nothing to do with the modifier...Vibration is normally a roller bearing problem, or if its more a HUMMING/ NOISE, that could be gear tooth pattern.

Could also be worn outboard bearing problem at the wheel, no necessarily inside the pumpkin.